Electromagnetic shift arrangement

ABSTRACT

An electromagnetic shift arrangement for a transmission ( 2 ) with gear wheels ( 4, 6 ) arranged on a gear shift ( 12 ) rotatable about an axis ( 20 ) which can be non-rotatably connected with the gear shaft ( 12 ) to form a ratio step via an axial movement of a shift dog ( 18 ) along the axis ( 20 ). An electromagnetic device ( 24, 26, 40 ) is provided which is adequate for axial movement of the shift dog ( 18 ) along the axis ( 20 ). The electromagnetic device ( 24, 26, 40 ) is disposed in the area of the shift dog ( 18 ) and acts upon the shift dog ( 18 ) directly without shift fork.

[0001] According to the preamble of claim 1 the invention relates to ashift arrangement for a vehicle transmission.

[0002] An electromagnetically activated shift arrangement for atransmission has been disclosed in U.S. Pat. No. 5,460,060. For eachratio pair to be shifted between which one shift arrangement is locatedthere is provided here a shift fork situated upon a rod and meshing in ashift dog. A gear shaft upon which are rotatably situated the gearwheels of the relevant ratio can be connected each time with one of thegear wheels by the axial movement of the shift dog. Upon the rod islocated the shift fork by means of which a respective laterally placedspring is forced to a middle position out of which it can be axiallymoved after activation of one magnet. The shift fork here moves axiallyopposite to the direction of the activated magnet. The ratio is switchedoff after termination of the activation of the magnet by the respectivespring. The shift arrangement has the disadvantage of being structurallydesigned with a high mass to be moved. The shift arrangement is switchedoff only by the tension of the springs provided.

[0003] The problem on which the invention is based is to overcome thedisadvantages of the prior art and show a shift arrangement in which themasses to be moved during the shift are as small as possible.

[0004] According to the invention an electromagnetic shift arrangementis proposed for a transmission having gear wheels rotatably disposedupon a gear shaft around an axis. To form a ratio step, the gear wheelsare non-rotatably connectable with the gear shaft by an axial movementof a shift dog along the axis of rotation of the gear shaft. The shiftarrangement also has an electromagnetic device suitable for axialmovement of the shift dog along the axis. The electromagnetic device issituated directly in the area of the shift dog and acts upon the shiftdog directly without assistance and intercalation of a shift fork. Theelectromagnetic device thus acts directly upon the shift dog and makespossible for a significant reduction of the masses to be moved duringthe shift operation. Experience has shown that relatively strong shiftforces are needed, especially for switching off a ratio step. Thedisconnecting forces needed depend on the masses to be shifted and onthe shifting speed that can be achieved. The smaller the masses to beshifted and the higher the shift speed achievable are, the smaller theshift force can be. In suitably dimensioned electromagnetic devices, itis thus possible to implement extremely short shift times which can beaccomplished specially in case of gear shifts in uneven roads. In onedevelopment, by adequate control of the electromagnetic device, it ispossible to adjust different load reduction times which ensure a longload reduction time, for example, in the course of an even road andshorter load reduction times in an inclination of the road without whichcontrol a disadvantageous speed decrease of the vehicle and in the mostunfavorable case a rolling back of the vehicle could be associated. Inone advantageous development, an electromagnetic device is provided foreach axial direction of movement along the axis of the gear shaft whichhas the gear wheels to be shifted. An advantageous embodiment of theinvention shows that the magnetic field to be generated in theelectromagnetic device is reversible in its action. It is thus possible,to implement a control of the magnetic fields in different operationaldirections in order to produce movements of the shift dog in bothdirections along the axis. This results in that in an advantageousdevelopment that only one electromagnetic device is provided for bothdirections of movement along the axis. In one development, by thecontrol of the magnetic fields, a reversal of the magnetic field can beproduced to form a damping device against an impact of the shift dog andin another advantageous development, the shift dog is kept in neutralposition by the electromagnetic device. In one embodiment, the shift dogis kept in neutral position by spring tension. One embodiment finallyshows that the electromagnetic devices are mounted fixed to the housingand electric feed lines are provided in or on the housing of thetransmission. The electromagnetic devices are magnetically insulated inrelation to parts of the transmission not to be shifted.

[0005] The invention is explained in detail with reference to a drawingwherein:

[0006]FIG. 1 shows two electromagnetic devices for two ratio steps; and

[0007]FIG. 2 shows one electromagnetic device for two ratio steps.

[0008]FIG. 1 shows a section from a transmission 2. A first gear wheel 4and a second gear wheel 6 are rotatably supported by bearings 8, 19 upona gear shaft 12. The gear wheels 4, 6 have one internal toothing 14, 16,respectively. A shift dog 18 is non-rotatable, but axially displaceablealong an axis 20 of the gear shaft 12. A disc 22 meshes in the shift dog18 or is designed integral therewith. Upon each side of the disc 22 issituated one electromagnetic device 24, 26, respectively, which isstationarily fixed to the housing of the transmission in a manner notshow here. The electromagnetic devices 24, 26 are connected with acontrol device 28. Between the electromagnetic devices 24, 26 and therelevant gear wheels 4, 6 one electromagnetic insulating disc 30 and 32is provided.

[0009] For non-rotatable connection of the gear wheel 4 with the gearshaft 12 and for the formation produced thereby of a ratio step of thetransmission 2, the shift dog 18 is axially displaceable to the leftalong the axis of the plane of the drawing. This occurs by control ofthe electromagnetic device 24 by the control device 28. Theelectromagnetic device generates a magnetic field by which the disc 22is drawn in direction to the gear wheel 4. An external toothing 34 onthe shift dog 18 then meshes in the internal toothing 14 of the gearwheel 4. Thereby the gear wheel 4 is non-rotatably connected with thegear shaft 12. To assist the movement of the shift dog 18 in directionto the gear wheel 4, the electromagnetic device 26 can also becontrolled. In the electromagnetic device 26 is likewise generated amagnetic field which is oriented so that it ejects the disc 22 indirection to the gear wheel 4. Thereby the electromagnetic devices canbe developed accordingly small or the shift force be accordinglyincreased.

[0010] To break up the non-rotatable connection, the electromagneticdevice 24 is controlled so that the disc 22 is ejected and thus thetoothing 34 of the shift dog 18 detaches itself from the toothing 14 ofthe gear wheel 4. It is also possible here to provide an adequateassistance by the electromagnetic device 26 by the magnetic field ofwhich the disc 22 is then drawn in direction to the gear wheel 6.

[0011] If the shift dog 18 should remain in the neutral position betweenthe two gear wheels 4, 6, this can take place by an adequate control ofboth electromagnetic devices 24 and 26. The two magnetic fields thengenerated can keep the disc 22 either in a drawing or an ejecting mannerand thus retain the shift dog 18 in a neutral intermediate position. Theintermediate position can also be brought about by two plate springs 36,38 lying between the disc 22 and the respective electromagnetic device24, 26. If the disc 22 moves in one or the other direction, the platesprings 36, 38 are accordingly compressed.

[0012] A connection of the gear wheel 6 with the gear shaft 12 byswitching off the neutral position accordingly occurs in inverse manner.

[0013]FIG. 2 shows a section from a transmission 2. A first gear wheel 4and a second gear wheel 6 are non-rotatably supported upon a gear shaft12 by the bearings 8, 10. The gear wheels 4, 6 have respective internaltoothings 14, 16. A shift dog 18 is non-rotatable, but axiallydisplaceable along an axis of rotation 20 of the gear shaft 12. A disc22 meshes in the shift dog 18 or is designed integral therewith. Uponone side of the disc 22 is situated an electromagnetic device 40 whichis stationarily fastened on the housing of the transmission in a mannernot shown here. The electromagnetic device 40 is connected with acontrol device 28. An electromagnetic insulating disc 42 is providedbetween the electromagnetic device 40 and the gear wheel 6.

[0014] In the plane of the drawing, the shift dog 18 is axiallydisplaced to the right along the axis 20 for non-rotatable connection ofthe gear wheel 6 with the gear shaft 12 and for the formation therebyproduced of a ratio step of the transmission 2. This occurs by thecontrol of the electromagnetic device 40 by the control device 28. Theelectromagnetic device 40 generates a magnetic field by which the disc22 is drawn in direction to the gear wheel 6. An external toothing 44 onthe shift dog 18 meshes then in the internal toothing 16 of the gearwheel 6 during synchronous rotational speeds of the shift dog 18 and thegear wheel 6. The gear wheel 6 is thereby non-rotatably connected withthe gear shaft 12.

[0015] To dissolve the non-rotatable connection, the electromagneticdevice 40 is controlled so that the disc 22 is ejected and thus thetoothing 44 of the shift dog 18 detaches itself from the toothing 16 ofthe gear wheel 6. A support by a plate spring 46 provided between disc22 and electromagnetic device 40 can result whereby the disc 22 isejected in direction toward the gear wheel 4.

[0016] If the shift dog 18 must be kept in the neutral position betweenboth gear wheels 4, 6, this can occur by an adequate control of theelectromagnetic device 40. The magnetic field then generated can keepthe disc 22 either in a drawing or an ejecting manner and thus the shiftdog 18 in a neutral intermediate position. The intermediate position canbe produced also by two plate springs 46,48. The plate spring 46 isbetween the disc 22 and the electromagnetic device 40 and the platespring 48 lies between the disc 22 and the gear wheel 4. When the disc22 moves in one or the other direction, the plate springs 46, 48 areaccordingly compressed.

[0017] The gear wheel 4 is connected with the gear shaft 12 by switchingoff from the neutral position by control of the electromagnetic device40 by the control device 28 in a manner such that an ejecting magneticfield is generated and the disc 22 and therewith the shift dog 18 isejected from the electromagnetic device 40 in direction to the gearwheel 4. The external toothing 34 on the shift dog 18 meshes then in theinternal toothing 14 of the gear wheel 4 during synchronous rotationalspeeds of the shift dog 18 and the gear wheel 4. Thereby the gear wheel4 is non-rotatably connected with the gear shaft 12. Reference numerals 2 transmission  4 gear wheel  6 gear wheel  8 bearing 10 bearing 12gear shaft 14 internal toothing 16 internal toothing 18 shift dog 20axis 22 disc 24 electromagnetic device 26 electromagnetic device 28control device 30 insulating disc 32 insulating disc 34 externaltoothing 36 plate spring 38 plate spring 40 electromagnetic device 42insulating disc 44 external toothing 46 plate spring 48 plate spring

1. Electromagnetic shift arrangement for a transmission (2) whichcomprises gear wheels (4, 6) rotatably disposed around an axis (20) on agear shaft (12) and which to form a ratio step can be non-rotatablyconnected with said gear shaft (12) by means of an axial movement of ashift dog (18) along said axis (20) and comprising an electromagneticdevice (24, 26, 40) adequate for axial movement of said shift dog (18)along said axis (20), characterized in that said electromagnetic device(24, 26, 40) is situated in the area of said shift dog (18) and withoutshift fork acts directly upon said shift dog (18).
 2. Electromagneticshift arrangement according to claim 1, characterized in that oneelectromagnetic device (24, 26) is provided for each axial direction ofmovement along said axis (20).
 3. Electromagnetic shift arrangementaccording to claim 1, characterized in that one electromagnetic device(40) is provided for both directions of movement along said axis (20).4. Electromagnetic shift arrangement according to claim 1 or 2,characterized in that during a shifting movement in axial direction bothelectromagnetic devices (24, 26) can be controlled independently of eachother in different operational directions of the magnetic fields. 5.Electromagnetic shift arrangement according to any one of claims 1 to 4,characterized in that the magnetic field to be generated in saidelectromagnetic device (24, 26, 40) is reversible in its operationaldirection for producing movements of said shift dog (18) along said axis(20) in both directions of movement.
 6. Electromagnetic shiftarrangement according to any one of claim 1 to 5, characterized in thatby control of said electromagnetic devices (24, 26, 40) different loadreduction times can be adjusted.
 7. Electromagnetic shift arrangementaccording to claim 5, characterized in that by means of the control areversal of the magnetic field is produced to form a damping deviceagainst an impact of said shift dog (18).
 8. Electromagnetic shiftarrangement according to any one of claim 1 to 7, characterized in thatsaid shift dog (18) is retained in a neutral position by saidelectromagnetic device (24, 26, 40).
 9. Electromagnetic shiftarrangement according to any one of claims 1 to 7, characterized in thatsaid shift dog (18) is retained in a neutral position by spring tension.10. Electromagnetic shift arrangement according to any one of claims 1to 9, characterized in that said electromagnetic device (24, 26, 40) ismounted fixed to the housing and electrical feed lines are provided inor on the housing of said transmission (2).
 11. Electromagnetic shiftarrangement according to any one of claims 1 to 10, characterized inthat said electromagnetic device (24, 26, 40) is magnetically insulatedin relation to the parts of said transmission (2) not to be moved.